Of diterpenes

Dlterpenes. Diterpenes contain 20 carbon atoms. The resin acids and Vitamin A are the most commercially important group of diterpenes. GibbereUic acid [77-06-5] (110), produced commercially by fermentation processes, is used as a growth promoter for plants, especially seedlings. 

While no examples were encountered in the steroid field which utilize this technique, it is well documented in the case of diterpenes. Ferruginol-3-one (79), for example, gives a hexadeuterio product (80) which after back... 

Mass spectrometry in structural investigation of diterpene alkaloids 97IZV1096. 

For the performance of an enantioselective synthesis, it is of advantage when an asymmetric catalyst can be employed instead of a chiral reagent or auxiliary in stoichiometric amounts. The valuable enantiomerically pure substance is then required in small amounts only. For the Fleck reaction, catalytically active asymmetric substances have been developed. An illustrative example is the synthesis of the tricyclic compound 17, which represents a versatile synthetic intermediate for the synthesis of diterpenes. Instead of an aryl halide, a trifluoromethanesul-fonic acid arylester (ArOTf) 16 is used as the starting material. With the use of the / -enantiomer of 2,2 -Z7w-(diphenylphosphino)-l,F-binaphthyl ((R)-BINAP) as catalyst, the Heck reaction becomes regio- and face-selective. The reaction occurs preferentially at the trisubstituted double bond b, leading to the tricyclic product 17 with 95% ee. °... 

Milanova R, M Moore, Y Hirai (1994) Hydroxylation of synthetic abietane diterpenes by Aspergillus and Cunninghamella species novel route to the family of diterpenes isolated from Tripterygium wilfordii. J Nat Prod 5T 882-889. 

Entries 10 to 14 show reactions involving acetals. Interestingly, Entry 10 shows much-reduced stereoselectivity compared to the corresponding reaction of the aldehyde (The BF3-catalyzed reaction of the aldehyde is reported to be 24 1 in favor of the anti product ref. 80, p. 91). There are no stereochemical issues in Entries 11 or 12. Entry 13, involving two cyclic reactants, gave a 2 1 mixture of stereoisomers. Entry Mis a step in a synthesis directed toward the taxane group of diterpenes. Four stereoisomeric products were produced, including the Z E isomers at the new enone double bond. 

This reaction can be used in synthesis of medium-sized rings by cleavage of specific bonds. An example of this reaction pattern can be seen in a fragmentation used to construct the ring structure found in the taxane group of diterpenes. 

Large amounts of diterpene mono- and di-alcohols have been found in both Arabic and Robusta coffees, including cafestol, kahweol, and 16-O-methylcafestol.126 The characteristic differences can be used to quantify the Robusta content of commercial blends with Arabica.127... 

Fujikawa et al. made the interesting observation that an extract from the stem bark given orally at a dose of 250 mg/kg once a day for 2 weeks protects rats against MPTP-induced Parkinsonian bradykinesia and catalepsy and inhibited neuronal loss of dopamine (70). The active constituents involved here are unknown. Note that the plant abounds with pentacyclic oleanene saponins (71-73). Note that Acanthopanax species are known to elaborate a series of diterpenes, a group that has the potency to bind to dopamine receptors, as reported in Vitex agnus-castus. Are diterpenes involved in the dopaminergic properties of Acanthopanax gracilistylus W. W. Sm. ... 

Scheme 2.73. Synthesis of diterpenes via domino acylation/cycloalkylation and alkylation/...

A recent example demonstrates that corals rely on induced biosynthesis of terpenes as a dynamic defense strategy as well. The induction of terpenoid secondary metabolites was observed in the sea whip Pseudopterogorgia elisabethae [162]. Levels of pseudopterosins 89-92, a group of diterpene glycosides with anti-inflammatory and analgesic properties (Scheme 23) [163-165], are increased in response predation by the mollusk Cyphoma gibbosum. First bioassays indicate that these natural products are involved in the chemical defense. 

C. R. Enzell, Mass spectrometric studies of diterpenes IV. Aromatic diterpenes, Tetrahedron Lett., 19, 2135 2143 (1966). 

In order to avoid experiments which are very long, the sampling time was fixed at 60 min. In these conditions, the partition equilibrium for diterpenes extraction is not achieved and SPME does not have maximum sensitivity. However, peak intensities are sufficiently high to detect the presence of diterpenes in a sample. Moreover, a proportional relationship exists between the amount of analyte adsorbed by the SPME fibre and its initial concentration in the sample matrix before reaching partition equilibrium [5, 59]. SPME quantifications are then feasible if necessary, by rigorously reproducing the experimental conditions. 

The first sample, dating from the Ptolemaic period ( 300 BC), was found in a container from a tomb from Fayoum. The volatile compounds observed in this sample (see Table 10.1, column 11) were very similar to those of pine pitch. The two chromatograms are presented in Figure 10.21. The major compounds are guaiacol (11) and its para-n-alkyl derivatives (24, 35, 43) and the degradation products of diterpenic acids 19-norabieta-8,l 1,13-triene (95), 18-norabieta-8,11,13-triene (100), 10,18-bisnorabieta-5,7,9(10),ll,13-pentaene (102), retene (105) and methyldehydroabietate (106). The major compounds observed after... 

D. Scalarone, M. Lazzari, O. Chiantore, Ageing behaviour and pyrolytic characterisation of diterpenic resins used as art materials colophony and Venice turpentine, J. Anal. Appl. Pyrol., 64, 345 361 (2002). 

Similarly, oxidation with DMD and KMn04 of diterpene alkaloids eldeline, talatizamine, aconitine, and zongorine has been carried out (95). 

Malacria and coworkers346 prepared phyllocladane and kaurane types of diterpenes by means of [3 + 2]/[2 + 2 + 2]/[4 + 2] cascade reaction sequences. A representative example of such a reaction sequence has been outlined in equation 171. The five-membered ring of 598 was built by a 1,3-dipolar cycloaddition between 596 and an all-carbon 1,3-dipole generated from 597. The reaction of 598b with 568h afforded benzocyclobutene 599. The intramolecular [4 + 2] cycloaddition afforded diastereomers 600 and 601 in a 5 1 ratio. It is noteworthy that the exocyclic double bond in 598b neither participates in the [2 + 2 + 2] cycloaddition reaction nor isomerizes under the reaction conditions applied. 

Pseudopterosins coexist with the seco-pseudopterosins, suggesting that these two classes of diterpenes are produced from a single cyclase product. Elisabethatriene (42) undergoes aromatization to erogorgiaene (1) presumably a series... 

Koul IB, Kapil A. (1994) Effect of diterpenes from Andrographis paniculata on antioxidant defense system and lipid peroxidation. Indian J Pharmacol 26 296-300. 

Abstract The isolation, structure and total synthesis of members of four classes of diterpenes has been summarized. Dolabellanes, neodolabellanes, dolastanes and neodolas-tanes are structurally related bi- or tricyclic diterpenes. Dolabellanes belong to a continuously growing class of diterpenes being isolated from marine and terrestrial sources. The published work on isolation and synthesis since 1998 has been summarized. Neodolabellanes represent a scarce class of diterpenes that have been isolated exclusively... 

The biosynthesis of diterpenes was created to produce molecular diversity. Literally hundreds of different macrocyclic, bicyclic and polycyclic diterpenes... 

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